1. Technical Field
Embodiments of the present disclosure relate to systems and methods for processing of hydrocarbon streams, such as heavy crude and/or bitumen, or process waste streams associated therewith. Yet other embodiments relate to comminuting solid particles in process streams, where comminution results in disintegrating the skeletal structure of the solid particles. Specific embodiments pertain to using a high shear device to comminute suspended solids in a process stream, where the solids have an initial internal porosity suitable for holding gas internally therein and a particle density, and wherein comminution of the solids moves the density toward skeletal density, releasing the trapped gas and reducing the internal porosity. Embodiments relate to the use of high shear in the separation of solids from feeds comprising bitumen and/or heavy crude oil, and the separation of water and mineral solids from tailings conventionally sent to a tailings pond. The separation may occur without the use of a gas or gas adjuvant.
2. Background of the Disclosure
Large deposits of heavy hydrocarbon sometimes referred to as bitumen are located in many countries around the world. Bitumen may be recoverable by means of secondary or tertiary recovery processes that involve heating, solubilization or mobility control. Many of these heavy hydrocarbon deposits contain high concentrations of asphaltenes that contribute to difficulties in recovery, transporting and upgrading. Oil sands, also, known as tar sands, are heavy hydrocarbons found in the United States, Canada, Russia, Venezuela, and various countries in the Middle East. Deposits in the oil sands of Alberta, Canada are the single-largest known source of petroleum in the world. These oil sands contain bitumen and as much as 17 wt % asphaltenes. The Orinoco oil belt in Venezuela is another large accumulation of bitumen. Additionally, heavy crudes produced all over the world typically contain some amount of asphaltenes.
Heavy crude oil or crude bitumen extracted from the earth is in a viscous, solid or semi-solid form that does not flow easily at normal oil pipeline temperatures, making it difficult to transport, and expensive to process into gasoline, diesel fuel, and other products. The economic recovery and utilization of heavy hydrocarbons, including bitumen, is a significant energy challenge. The demand for heavy crudes, such as those extracted from oil sands, has increased significantly due to dwindling reserves of conventional lighter crude. These heavy hydrocarbons, however, are typically located in geographical regions far removed from existing refineries. Consequently, the heavy hydrocarbons are often transported via pipelines to refineries. In order to transport heavy crudes in pipelines they must meet pipeline quality specifications.
Extraction techniques utilized to recover bitumen may be broken down into three major categories: (1) those which employ water, either hot or cold, to float the bitumen oils away from the tar sands, (2) those which employ an organic solvent to dissolve the bitumen oils, and (3) those that involve heat. Extraction of bitumen may be either by removing the deposits from the ground and extracting the bitumen externally or by in situ extraction, where only the bitumen is removed and the mineral components are left in the ground. Processes utilizing water often involve air floatation, and typically involve the utilization of an alkaline material. Due to the formation of stable emulsions containing fine tar sands ore particles, water and bitumen oils, water-based processes are not particularly efficient, especially on ore of lower bitumen content. The treatment of emulsions comprising large volumes of water, bitumen oils and fine tar sands ore particles has proven to be challenging.
Extraction of bitumen using heat can be done with electric, steam or other form of heaters as described, for example, in U.S. Pat. App. Nos. 2008/0135253 and 2009/0095480 by Vinegar et al. Various combinations of extraction techniques can be used to extract bitumen in situ. It is generally believed that in situ extraction will be more cost effective than surface mining, although the predominant method of bitumen extraction used today is surface mining. Another solvent extraction technique under development involves the utilization of solvents (in the absence of water) and is similar to techniques utilized in oil seed extraction processes. Percolation and immersion-type extractors have been used, but the need for special designs and scale-up for processing of abrasive tar sands make economical extraction difficult. For example, the solvent to bitumen ratio needed for efficient extraction is generally high, up to 10:1, producing concomitantly high capital and utilities costs for recovery of the solvent via, for example, distillation. For economy of solvent utilization, spent sands must be stripped of residual solvent prior to disposal. Stripping of residual solvent is a capital and energy intensive undertaking.
Existing solvent extraction methods for dissolving bitumen oils from tar sands, for example, as disclosed in U.S. Pat. No. 4,160,718 issued to Rendall, typically involve environmentally unacceptable losses of solvent and additional problems associated with the hazards posed by the necessary storage of large solvent inventories and the need for large quantities of water. Other solvent, hot water, and combination extraction processes are disclosed in U.S. Pat. No. 4,347,118 to Funk et al. and U.S. Pat. No. 3,925,189 to Wicks, III. These methods all have commercial and/or ecological drawbacks, rendering them undesirable. A method that utilizes both solvent and hot water for extraction of bitumen from tar sands is the subject of U.S. Pat. No. 4,424,112 to Rendall.
Bitumen extraction techniques that do not involve solvent conventionally utilize truck and shovel operations. In such operations, the oil sand is first mined and then is delivered to a crusher. In one such process, bitumen separation and recovery from the oil sand are accomplished by following what is known as the Clark hot water extraction process. In the front end of this process, crushed oil sand is mixed with hot water and caustic in a rotating tumbler or conditioned in a hydrotransport line to produce an aqueous slurry. In the tumbler or hydrotransport line, bitumen globules contact and coat air bubbles that are entrained in the slurry. The slurry is then screened to remove large rocks and the like. The screened slurry is diluted with additional water, and the product is then temporarily retained in a primary separation vessel (PSV). In the PSV, the buoyant, bitumen-coated air bubbles rise through the slurry and form bitumen froth. The sand in the slurry settles and is discharged from the base of the PSV, together with some water and bitumen. This stream or a portion thereof is referred to as the ‘PSV underflow’ or tailings. A ‘middlings’ portion comprising water, non-buoyant bitumen, and fines may be collected from the middle of the PSV. The froth overflows the lip of the PSV and is recovered as the primary froth, which typically comprises about 60 weight percent bitumen, about 30 weight percent water and about 10 weight percent particulate solids.
The PSV underflow is introduced into a deep cone vessel, referred to as the tailings oil recovery vessel (‘TORV’). Here the PSV underflow is contacted and mixed with a stream of aerated middlings from the PSV. Again, bitumen and air bubbles contact and unite to form buoyant globules that rise and form froth. This ‘secondary’ froth overflows the lip of the TORV and is recovered. The secondary froth typically comprises about 45 weight percent bitumen, about 45 weight percent water and about 10 weight percent solids. The stream of middlings from the TORV is withdrawn and processed in a series of sub-aerated, impeller-agitated flotation cells. Secondary froth, typically comprising about 40 weight percent bitumen, about 50 weight percent water and about 10 weight percent solids, is produced from these cells.
The primary and secondary froth streams are typically combined to yield a product froth stream, often comprising about 60 weight percent bitumen, about 32 weight percent water and about 8 weight percent solids. The water and solids in the froth are contaminants which need to be reduced in concentration before the froth can be treated in a downstream refinery-type upgrading facility. This cleaning operation is generally carried out using what is referred to as ‘froth treatment.’
While there are a variety of froth treatment processes, all of these processes include deaeration of the combined froth product, followed by dilution with sufficient solvent, typically naphtha, to provide a solvent to froth (‘S/F’) ratio of about 0.40 (w/w). This is done to increase the density differential between the diluted bitumen on the one hand and the water and solids on the other. By way of example, Kizior (U.S. Pat. No. 4,383,914), Guymon (U.S. Pat. No. 4,968,412), Shelfantook et al. (Canadian Pat. No. 1,293,465), Birkholz et al. (Canadian Pat. No. 2,232,929), Tipman et al. (Canadian Pat. No. 2,200,899), Tipman et al. (Canadian Pat. No. 2,353,109), Mishra et al. (U.S. Pat. No. 6,019,888), Cymerman et al. (U.S. Pat. No. 6,746,599), Beetge et al. (U.S. Pat. App. 20060196812, and Graham et al. (U.S. Pat. No. 5,143,598) describe ways of processing and treating the froth produced during the extraction process.
A serious problem, however, in using a solvent extraction process to remove bitumen from such a carbonaceous solid is that fines, primarily particles less than 50 microns in diameter, are carried over in the solvent-dissolved bitumen extract. Failure to remove the fines results in an undesirable high-ash bitumen product as well as problems with plugging of equipment used in the separation process, especially, for example, filtration equipment. Similar problems arise when other carbonaceous liquids besides bitumen, such as coal liquid or shale oil, are used. Removal of the fines during recovery of the bitumen, from a carbonaceous solid or from a previously recovered carbonaceous liquid, is therefore important in providing a desirable low-ash liquid product and in minimizing fouling and plugging of equipment used in the process. It would be highly desirable to develop an extraction method for recovering bitumen from the aforesaid carbonaceous solids, and for removing fines from the aforesaid carbonaceous liquids which would permit control of the solvency power of the extraction solvent so as to maximize the amount of bitumen or other carbonaceous liquid recovered, and to minimize the fines content therein.
Following extraction of bitumen, a diluent, such as light naphtha, is often added for transportation. The naphtha must be distilled and recycled, adding to energy costs. Changes in temperature and/or composition may cause the asphaltenes to fall out of solution, thus necessitating pipeline cleaning. Typically, removal of asphaltenes desirably removes some of the heavy metals and sulfur associated with crude oil. It is well known that asphaltenes can be separated from bitumen or asphaltenic crude oil by precipitation with paraffinic solvents such as pentane or heptanes (see, for example, U.S. Pat. App. 2006/0260980 to Yeung; U.S. Pat. App. 2008/0245705 to Siskin et al.; U.S. Pat. No. 5,326,456 to Brons et al.; U.S. Pat. No. 5,316,659 to Brons et al.; U.S. Pat. No. 4,699,709 to Peck et al.; and U.S. Pat. No. 4,596,651 to Wolff et al.). Additionally, various settling aids and/or flocculants have been utilized to enhance the separation of asphaltenes (see, for example, U.S. Pat. App. 2006/0196812 to Beetge et al.).
It is conventionally believed that a high solvent to oil ratio (e.g., on the order of 40:1 by volume) is required to separate substantially-pure asphaltenes from bitumen or asphaltic crude oil. At lower solvent levels, commonly used in solvent deasphalting, substantial non-asphaltenic material precipitates with the asphaltenes, resulting in undesirable oil losses. Furthermore, solvent deasphalting relies on multiple theoretical stages of separation of barely immiscible hydrocarbon liquids, and such stages are intolerant to the presence of water. The oil yield of solvent deasphalting is also limited by the high viscosity of the resultant asphaltic materials, particularly for high viscosity bitumen feeds. It is thus difficult to obtain high quality oil with high oil yield due to the difficulties in achieving clean separation of the oil and asphaltic fractions. In solvent deasphalting, asphalt (essentially asphaltenes with residual oil) is produced as a very viscous, hot liquid, which forms glassy solids when cooled. This viscous liquid must be heated to a high temperature in order to be transportable, causing fouling and plugging limitations.
Another technique for removal of asphaltenes involves breaking a froth of extra heavy oil and water with heat and a diluent solvent, such as naphtha. In the case of paraffinic naphtha, partial asphaltene removal results. However, only about 50% of the asphaltenes may be readily removed with this treatment even with multiple stages, and complete removal of asphaltenes is thus not practical. Therefore, the resulting oils must be further processed by utilizing capital intensive technology that is relatively tolerant to asphaltenes.
It is also typical for hydrocarbon streams, such as shale oil and bitumen streams, to have solids (e.g., solid particles, solid component, etc.) suspended therein that have huge internal porosity and a lot of internal gas. The particle density of such solids may be orders of magnitude greater than the skeletal density, making it difficult to fully separate and/or settle solids from the hydrocarbon stream.
Despite the development of the above mentioned froth and solvent extraction processes, there remains a need for improved systems and processes of extracting bitumen of higher quality, for example, containing less water, less solids, less asphaltenes and/or less diluent. It would be desirable if the enhanced systems and processes would allow increased bitumen recovery, for example, by reducing oil losses during asphaltene removal and/or reduced oil losses in the tailings. There is also a need in the art for a method of selectively and efficiently removing asphaltenic contaminants from heavy oil, which mitigates the above-mentioned difficulties of the prior art. It would be even further desirable if the systems and processes would allow bitumen extraction and/or asphaltene removal without requiring high solvent and/or water-to-bitumen ratios, long residence times, gas adjuvants, and/or numerous or expensive processing units. Such systems and processes should desirably facilitate recycle, and thus economy of utilization, of process water and/or conditioning agents, such as base (e.g., caustic) and/or bicarbonate. It would be desirable to be able to separate solids with large internal porosities from hydrocarbon streams in an economical and expedient manner.